Duncan's next key role was in the 1992 science fiction film Split Second, with Rutger Hauer. He continued with guest roles on TV series and he appeared in other films such as War Dogs, Trick of the Eye, Dazzle (1995) and Tower of Terror.

Duncan was one of 400 actors considered for the lead role in the international hit series Highlander: The Series but lost out to Adrian Paul. He later guest-starred in the fifth season, in the episode "Dramatic License" as immortal Terence Coventry.